UK royals release Prince George's fourth birthday portrait

George, the great grandson of Queen Elizabeth, is third-in-line to the throne

Prince George's official fourth birthday portrait, taken in June 2017 at Kensington Palace in London and released on July 21, 2017. Chris Jackson / Getty Images via AP

Britain's Prince William and his wife, Kate, have released a portrait to mark the fourth birthday on Saturday of their son, Prince George.

George, the great grandson of Queen Elizabeth and third-in-line to the throne, is pictured with a beaming, toothy grin, while wearing a stripy blue shirt.

The portrait was taken last month by a professional photographer. In the past, Kate has released personal photos of the children, including ones of George captured in November 2014 ahead of Christmas. Another showed George with his sister, Princess Charlotte, in June 2015, one month after her birth.

George's first day of nursery was also captured by his parents and released to the public.

"The Duke and Duchess are very pleased to share this lovely picture as they celebrate Prince George's fourth birthday, and would like to thank everyone for all of the kind messages they have received," William's office said.

William and Kate, who are officially known as the Duke and Duchess of Cambridge, returned to England with George and his sister, now two years old, on Friday after a five-day tour of Poland and Germany.

The tour, which coincided with the second round of Brexit negotiations, was seen as a charm offensive meant to shore up relations with EU countries before Britain leaves the bloc.

The couple and their children delighted crowds in the two countries, but one regional German newspaper said the royals could do little to ease the pain of the divorce with the European Union.

"William and Kate supposed to smile Brexit away in Germany," ran the headline in the Rheinische Post.

In Germany, George toured a helicopter similar to the one his father has flown as a rescue pilot in the UK. His parents, meanwhile, were focused on Brexit.

In Berlin on Wednesday, Prince William said that Britain and Germany would remain close even after the UK breaks away from the EU.

"This relationship between the United Kingdom and Germany really matters," he said at an evening garden party.

"It will continue despite Britain’s recent decision to leave the European Union and I’m confident we shall remain the firmest of friends.”

Prince George is no stranger to diplomacy. In April 2016, he was pictured meeting then US president Barack Obama while wearing a dressing gown